Narrow Results

The influence of pump direction in all-optical gain-clamped fiber Raman amplifier using the directional couplers in feedback loop is demonstrated. The isolator direction decided the lasing direction in feedback loop. The comparison of performance in two lasing directions for both schemes is shown. It is concluded that the forward pumping configuration with forward lasing has better gain clamping performance and noise performance.

The effect of injecting of C-band amplified spontaneous emission (ASE) from C-band erbium-doped fiber amplifier (EDFA) on the performance of L-band EDFA is demonstrated using a circulator and broadband fiber Bragg grating (FBG). Injecting a large amount of ASE (VOA=0 dB) clamps the gain at 15.2 dB from -40 to -10 dBm with a gain variation of less than 0.3 dB. Injecting a small amount of ASE (attenuation of 20 dB and above) improves the small signal gain with a negligible noise figure penalty compared to that of an amplifier without the ASE injection. A maximum gain improvement of 3.5 dB is obtained at an attenuation of 20 dB. These results show that the ASE injection technique can be used either for gain improvement or gain clamping in L-band EDFA.